Murphy Sentinel 300P Series Programmable Switch Mode Battery Charger

Programmable charger for engine starting and standby batteries

The Murphy Sentinel SNTL300P is the base model of the Sentinel 300P Series of programmable switch mode battery chargers from Enovation Controls. The series provides DC power control, monitoring and protection for stationary engine starting and standby battery applications. It is offered either as an open-frame, UL-recognized module for mounting in an existing control panel, or as a UL-listed, wall-mounted stainless steel enclosure with LCD and analog metering options.

Charging features are multistage (float, bulk, absorption and AutoBoost), low output ripple below 1 percent, and optional temperature compensation. AutoBoost triggers on low charge or by remote switch and temporarily raises the charge voltage before returning to float, equalizing cells without overcharge and gassing. A battery-mounted sensor lets the charger adjust output voltage with temperature.

Technical specifications

Values are from Enovation Controls bulletin 1010705, revision 2017/02/09.

Models and part numbers

The bulletin lists SNTL300P (42703850) as the open-frame unit with a protective cover for 110/120/220/240 VAC input and 10 A at 12 or 24 V output. SNTL300PC (42703852) adds CAN/J1939 communication. ESNTL300PM (42703879) is the enclosed unit with an analog ammeter and voltmeter, and ESNTL300PCLM (42703875) adds an LCD for readout and configuration. Accessories include the SNTL-RTC remote temperature sensor with a 3 m lead (42703900), the SNTL300P-PCSUITE software and the SNTL300P-PCCONN PC connection kit.

Programming is by circuit board links or PC-based software. All models include RS485 communication for configuration and control, and an optional DIN rail clip is listed. Wiring is by screw terminal blocks, with knockouts for cable glands on the enclosed versions.

Matching the charger to the battery bank

The calibration table sets float and boost voltages by battery type at 20 C, for example 13.5 V float and 14.1 V boost for a 6 cell wet lead acid battery on the 12 V setting, and 27.0 V float and 28.2 V boost for 12 cells on the 24 V setting. NiCd, VRLA AGM and gel batteries have their own values. With the sensor connected, output varies by 3 mV per cell per degree C from 20 C within the range -10 to 50 C.

Dimensions and weights for the open-frame and enclosed versions are in the bulletin drawings and are not repeated here. Confirm the battery chemistry, cell count, AC supply, mounting style, need for CAN/J1939 and whether temperature compensation is wanted before ordering. Mount with the air clearances stated in the bulletin. Enovation Controls lists this product family on its Legacy Products page, which describes those items as less popular or outdated but still available for purchase. Confirm current availability and any replacement part before ordering.

Installation of the Sentinel 300P

Decide early whether the open-frame module or one of the enclosed units fits the job. The open-frame version suits a generator control panel that already provides protection and ventilation, while the enclosed versions suit a wall position in the generator room. In both cases, route the AC supply, the DC output to the battery and the low-voltage alarm wiring separately, size the DC cables for the charging current and the cable run, and protect the circuits as required by the panel design and local wiring rules. Keep the battery cables short and tidy, and make sure polarity at the battery and at the charger terminals is checked twice before connection. If temperature compensation is used, fit the remote sensor on or close to the battery as the bulletin describes, not in the charger enclosure.

Commissioning checklist

Before switching on, confirm that the programmed system voltage and the float and boost settings correspond to the actual battery chemistry and cell count, using the calibration table as the reference. After switching on, measure the DC output at the battery terminals with a calibrated meter, compare it with the programmed value and note the reading in the commissioning record. Test each relay output that is wired to the generator controller or building management system by creating the condition or using a simulation where safe, so that charge fail, AC fail and battery voltage alarms are proven at the receiving end and not only at the charger. If RS485 or CAN/J1939 communication is used, confirm that the receiving device reads the expected values.

Periodic maintenance

A standby battery charger is only as useful as the battery it maintains. Include both in the generator maintenance routine: check terminal tightness and cleanliness, look for corrosion or electrolyte residue on wet cells, compare charger output with the recorded commissioning value, and confirm that alarms still reach the control room. Battery testing intervals and electrolyte checks should follow the battery manufacturer’s instructions and any standby power standard the site applies.

Generator rooms in Oman and the GCC

Standby generators in the Gulf are often housed in rooms or acoustic enclosures that become very hot during summer, especially while the engine is running. Compare the expected temperature at the charger and at the battery with the operating range in the bulletin, and remember that battery life in general is shortened by sustained high temperature, which is one reason temperature compensation is worth considering on these sites. Keep the charger away from engine exhaust and radiator discharge air, maintain the stated air clearances, and keep dust off ventilation paths during routine cleaning. In humid coastal sites, inspect terminals and cable glands for signs of moisture or corrosion.

Documents and quotation

The attached bulletin 1010705 is the source for the values above. Seven Star LLC supplies Murphy products as an independent supplier in Muscat. Send the model code, battery type and voltage, supply and quantity with your enquiry. Related items appear under UPS and batteries.